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X-CSE-ConnectionGUID: vaUuFdQ6RjOQ4lkRSGic4g== X-CSE-MsgGUID: ki3Xcx5SSdKcVLxPIU6KCA== X-IronPort-AV: E=McAfee;i="6800,10657,11892"; a="92546902" X-IronPort-AV: E=Sophos;i="6.25,255,1779174000"; d="scan'208";a="92546902" Received: from orviesa001.jf.intel.com ([10.64.159.141]) by orvoesa106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Sep 2026 02:47:54 -0700 X-CSE-ConnectionGUID: fV2Zhz8TSAW2Arb2x6ej0w== X-CSE-MsgGUID: 2maLF6D4Rr6e+knV4AZ/ug== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,255,1779174000"; d="scan'208";a="307263818" Received: from unknown (HELO [10.238.2.33]) ([10.238.2.33]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Sep 2026 02:47:40 -0700 Message-ID: Date: Tue, 1 Sep 2026 17:47:37 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v12 09/45] KVM: guest_memfd: Stub in ability to enable in-place shared<=>private conversion To: ackerleytng@google.com Cc: aik@amd.com, andrew.jones@linux.dev, brauner@kernel.org, chao.p.peng@linux.intel.com, david@kernel.org, jmattson@google.com, jthoughton@google.com, michael.roth@amd.com, oupton@kernel.org, pankaj.gupta@amd.com, qperret@google.com, rick.p.edgecombe@intel.com, rientjes@google.com, shivankg@amd.com, steven.price@arm.com, willy@infradead.org, wyihan@google.com, yan.y.zhao@intel.com, forkloop@google.com, pratyush@kernel.org, suzuki.poulose@arm.com, aneesh.kumar@kernel.org, liam@infradead.org, Paolo Bonzini , Sean Christopherson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Jonathan Corbet , Shuah Khan , Shuah Khan , Vishal Annapurve , Andrew Morton , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Youngjun Park , Qi Zheng , Shakeel Butt , Kiryl Shutsemau , Baoquan He , Jason Gunthorpe , John Hubbard , Peter Xu , tarunsahu@google.com, Randy Dunlap , Lorenzo Stoakes , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Fuad Tabba , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev, Xiaoyao Li References: <20260830-gmem-inplace-conversion-v12-0-85e5fd25252a@google.com> <20260830-gmem-inplace-conversion-v12-9-85e5fd25252a@google.com> Content-Language: en-US From: Binbin Wu In-Reply-To: <20260830-gmem-inplace-conversion-v12-9-85e5fd25252a@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: B2CB8C0002 X-Stat-Signature: t1yfc6zs8u5rcnajty331uka3tu4wemt X-Rspam-User: X-HE-Tag: 1788256075-522945 X-HE-Meta: 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 sgDDLkgB xkG6UDXlRzdFUHgGiFY24AdvhPa3UflSYh7xbuNWClG/Km7SaJaSq4yr0GKAqcwN8f1ug8GZK9KFqCmUEu6bGudzZAF5rzQVC8aBe/0SeifqhQQrS+h44yECGxUCYDSvaD8x0/FPcz6uBVH4VtO7EJkXZeRPQ3PKjo8xBlhyI3MuuWzcSJWxUq0/avA0mmJk6eesiYiu2IjOqJs1zPsTH09eURiYvYtC0e4AVZm8ZgttpOczLzDa/jku4EiPnhFeExLuwYNbeiz6LQ8r3OApvAoXlxLOubWd5nQ+oGXaAKPjo655jydTOvA1r/wBsFPwX+M5nT09WLw25/Nwr9ezHqQHf7Q== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/31/2026 8:25 AM, Ackerley Tng via B4 Relay wrote: > From: Sean Christopherson > > Stub in global variable to enable in-place guest_memfd private<=>shared > memory conversion, which will eventually be exposed to userspace via a > module param, and wire up the __kvm_is_private_gfn() static call to the > guest_memfd version when in-place conversion is enabled, i.e. when gmem is > the sole authority on private vs. shared memory. > > Cc: Fuad Tabba > Cc: Xiaoyao Li > Signed-off-by: Sean Christopherson > Co-developed-by: Ackerley Tng > Signed-off-by: Ackerley Tng Reviewed-by: Binbin Wu One nit below. > --- > Documentation/virt/kvm/api.rst | 7 +++++++ > include/linux/kvm_host.h | 6 ++++++ > virt/kvm/guest_memfd.c | 26 ++++++++++++++++++++++++++ > virt/kvm/kvm_main.c | 12 +++++++++++- > 4 files changed, 50 insertions(+), 1 deletion(-) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index e0430cc750c9e..90a29424c54c8 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -6382,6 +6382,11 @@ KVM_SET_USER_MEMORY_REGION2, e.g. shared memory can be lazily mapped/allocated > on-demand. > > When mapping a gfn into the guest, KVM selects shared vs. private, i.e consumes > +userspace_addr vs. guest_memfd, based on the state in guest_memfd, which is the > +sole authority on private vs. shared memory. See :ref:`KVM_CREATE_GUEST_MEMFD` > +to find out more about the creation-time shared/private status. > + > +If in-place conversion is disabled, KVM selects shared vs. private, i.e consumes Nit: i.e -> i.e. > userspace_addr vs. guest_memfd, based on the gfn's KVM_MEMORY_ATTRIBUTE_PRIVATE > state. At VM creation time, all memory is shared, i.e. the PRIVATE attribute > is '0' for all gfns. Userspace can control whether memory is shared/private by > @@ -6429,6 +6434,8 @@ the state of a gfn/page as needed. >